SID-Maths:
Frequency:
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To calculate the frequency corresponding to the 16-bit value in
$D400+$D401, $D407+$D408, $D40E+$D40F use the following formula:
Freq = 16Bit-Value * Phi2 / 16777216 Hz
where Phi2 is the system-clock, 985248 Hz for PAL-systems,
1022727 Hz for NTSC-systems.
A good approximation for both systems is the formula:
Freq = 16Bit-Value / 17.03
Pulse-Width:
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To calculate the pulse width (in %) corresponding to the 12-bit value in
$D402+$D403, $D409+$D40A, $D410+$D411 use the following formula:
PulseWidth = (16Bit-Value / 40.96) %